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Publications (10 of 61) Show all publications
Li, Y., Armitage, S., Stevens, T. & Meng, X. (2018). Alluvial fan aggradation/incision history of the eastern Tibetan plateau margin and implications for debris flow/debris-charged flood hazard. Geomorphology, 318, 203-216
Open this publication in new window or tab >>Alluvial fan aggradation/incision history of the eastern Tibetan plateau margin and implications for debris flow/debris-charged flood hazard
2018 (English)In: Geomorphology, ISSN 0169-555X, E-ISSN 1872-695X, Vol. 318, p. 203-216Article in journal (Refereed) Published
Abstract [en]

This paper reconstructs the Quaternary aggradation and incision history of a debris flow/debris-charged flood-affected valley in order to detect the impact of climate on alluvial fan dynamics. We used optically stimulated luminescence (OSL) dating of quartz to determine the ages of alluvial fan terraces. Comparison between the aggradation and incision history and regional climatic records suggests that aggradation occurred in cold and/or dry climates, whereas incision is a feature of warm and wet climates. Cold climates lead to enhanced frost shattering, and dry climates cause deteriorated vegetation. Both effects caused surplus sediment which was transported by infrequent flood discharges to form alluvial fan/terrace deposits. Incision during wet and warm climates is due to increased vegetation cover and an increase in the frequency of flood discharges. This relationship between climate and valley evolution is applied to assess future changes in the present active channel by considering recent climatic records. The results show that the valley channel is expected to experience net incision if the average temperature continues increasing while precipitation maintains at a constant level.

National Category
Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:uu:diva-360500 (URN)10.1016/j.geomorph.2018.06.016 (DOI)000442191600015 ()
Available from: 2018-09-13 Created: 2018-09-13 Last updated: 2018-10-03Bibliographically approved
Schaetzl, R. J., Bettis, E. A., Crouvic, O., Fitzsimmons, K. E., Grimley, D. A., Hambach, U., . . . Zech, R. (2018). Approaches and challenges to the study of loess: Introduction to the Loess-Fest Special Issue. Quaternary Research, 89(3), 563-618
Open this publication in new window or tab >>Approaches and challenges to the study of loess: Introduction to the Loess-Fest Special Issue
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2018 (English)In: Quaternary Research, ISSN 0033-5894, E-ISSN 1096-0287, Vol. 89, no 3, p. 563-618Article in journal, Editorial material (Other academic) Published
Abstract [en]

In September 2016, the annual meeting of the International Union for Quaternary Research's Loess and Pedostratigraphy Focus Group, traditionally referred to as a LoessFest, met in Eau Claire, Wisconsin, USA. The 2016 LoessFest focused on thin loess deposits and loess transportation surfaces. This LoessFest included 75 registered participants from 10 countries. Almost half of the participants were from outside the United States, and 18 of the participants were students. This review is the introduction to the special issue for Quaternary Research that originated from presentations and discussions at the 2016 LoessFest. This introduction highlights current understanding and ongoing work on loess in various regions of the world and provides brief summaries of some of the current approaches/strategies used to study loess deposits.

Keywords
Loess
National Category
Geology
Identifiers
urn:nbn:se:uu:diva-358131 (URN)10.1017/qua.2018.15 (DOI)000432179700001 ()
Available from: 2018-08-28 Created: 2018-08-28 Last updated: 2018-08-28Bibliographically approved
Stevens, T., Buylaert, J.-P., Thiel, C., Ujvari, G., Yi, S., Murray, A., . . . Lu, H. (2018). Ice-volume-forced erosion of the Chinese Loess Plateau global Quaternary stratotype site. Nature Communications, 9, Article ID 983.
Open this publication in new window or tab >>Ice-volume-forced erosion of the Chinese Loess Plateau global Quaternary stratotype site
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2018 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 9, article id 983Article in journal (Refereed) Published
Abstract [en]

The International Commission on Stratigraphy (ICS) utilises benchmark chronostratigraphies to divide geologic time. The reliability of these records is fundamental to understand past global change. Here we use the most detailed luminescence dating age model yet published to show that the ICS chronology for the Quaternary terrestrial type section at Jingbian, desert marginal Chinese Loess Plateau, is inaccurate. There are large hiatuses and depositional changes expressed across a dynamic gully landform at the site, which demonstrates rapid environmental shifts at the East Asian desert margin. We propose a new independent age model and reconstruct monsoon climate and desert expansion/contraction for the last ~250 ka. Our record demonstrates the dominant influence of ice volume on desert expansion, dust dynamics and sediment preservation, and further shows that East Asian Summer Monsoon (EASM) variation closely matches that of ice volume, but lags insolation by ~5 ka. These observations show that the EASM at the monsoon margin does not respond directly to precessional forcing.

National Category
Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:uu:diva-346111 (URN)10.1038/s41467-018-03329-2 (DOI)000426899300006 ()29515117 (PubMedID)
Available from: 2018-03-14 Created: 2018-03-14 Last updated: 2018-05-22Bibliographically approved
Fenn, K., Stevens, T., Bird, A., Limonta, M., Rittner, M., Vermeesch, P., . . . Lin, Z. (2018). Insights into the provenance of the Chinese Loess Plateau from joint zircon U-Pb and garnet geochemical analysis of last glacial loess. Quaternary Research, 89(3), 645-659
Open this publication in new window or tab >>Insights into the provenance of the Chinese Loess Plateau from joint zircon U-Pb and garnet geochemical analysis of last glacial loess
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2018 (English)In: Quaternary Research, ISSN 0033-5894, E-ISSN 1096-0287, Vol. 89, no 3, p. 645-659Article in journal (Refereed) Published
Abstract [en]

The Chinese Loess Plateau, the world's largest and oldest loess record, preserves evidence of Asia's long-term dust source dynamics, but there is uncertainty over the source of the deposits. Recent single-grain detrital zircon U-Pb age analysis has progressed this issue, but debates remain about source changes, and the generation and interpretation of zircon data. To address this, we analyze different groupings of new and existing datasets from the Loess Plateau and potential sources. We also present the results of a first high resolution sampling, multi-proxy provenance analysis of Beiguoyuan loess using U-Pb dating of detrital zircons and detrital garnet geochemistry. The data shows that some small source differences seem to exist between different areas on the Loess Plateau. However, sediment source appears to be unchanging between loess and palaeosols, supporting a recent material recycling hypothesis. Our zircon and garnet data demonstrates, however, that Beiguoyuan experienced a temporary, abrupt source shift during the last glacial maximum, implying that local dust sources became periodically active during the Quaternary. Our results highlight that grouping data to achieve bigger datasets could cause identification of misleading trends. Additionally, we suggest that multi-proxy single-grain approaches are required to gain further insight into Chinese Loess Plateau dust sources.

National Category
Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:uu:diva-337563 (URN)10.1017/qua.2017.86 (DOI)000432179700004 ()
Available from: 2018-01-02 Created: 2018-01-02 Last updated: 2018-07-31Bibliographically approved
Giosan, L., Naing, T., Tun, M. M., Clift, P. D., Filip, F., Constantinescu, S., . . . Thwin, S. (2018). On the Holocene evolution of the Ayeyawady megadelta. Earth Surface Dynamics, 6(2), 451-466
Open this publication in new window or tab >>On the Holocene evolution of the Ayeyawady megadelta
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2018 (English)In: Earth Surface Dynamics, ISSN 2196-6311, Vol. 6, no 2, p. 451-466Article in journal (Refereed) Published
Abstract [en]

The Ayeyawady delta is the last Asian megadelta whose evolution has remained essentially unexplored so far. Unlike most other deltas across the world, the Ayeyawady has not yet been affected by dam construction, providing a unique view on largely natural deltaic processes benefiting from abundant sediment loads affected by tectonics and monsoon hydroclimate. To alleviate the information gap and provide a baseline for future work, here we provide a first model for the Holocene development of this megadelta based on drill core sediments collected in 2016 and 2017, dated with radiocarbon and optically stimulated luminescence, together with a reevaluation of published maps, charts and scientific literature. Altogether, these data indicate that Ayeyawady is a mud-dominated delta with tidal and wave influences. The sediment-rich Ayeyawady River built meander belt alluvial ridges with avulsive characters. A more advanced coast in the western half of the delta (i.e., the Pathein lobe) was probably favored by the more western location of the early course of the river. Radiogenic isotopic fingerprinting of the sediment suggests that the Pathein lobe coast does not receive significant sediment from neighboring rivers. However, the eastern region of the delta (i.e., Yangon lobe) is offset inland and extends east into the mudflats of the Sittaung estuary. Wave-built beach ridge construction during the late Holocene, similar to several other deltas across the Indian monsoon domain, suggests a common climatic control on monsoonal delta morphodynamics through variability in discharge, changes in wave climate or both. Correlation of the delta morphological and stratigraphic architecture information on land with the shelf bathymetry, as well as its tectonic, sedimentary and hydrodynamic characteristics, provides insight on the peculiar growth style of the Ayeyawady delta. The offset between the western Pathein lobe and the eastern deltaic coast appears to be driven by tectonic-hydrodynamic feedbacks as the extensionally lowered shelf block of the Gulf of Mottama amplifies tidal currents relative to the western part of the shelf. This situation probably activates a perennial shear front between the two regions that acts as a leaky energy fence. Just as importantly, the strong currents in the Gulf of Mottama act as an offshore-directed tidal pump that helps build the deep mid-shelf Mottama clinoform with mixed sediments from the Ayeyawady, Sittaung and Thanlwin rivers. The highly energetic tidal, wind and wave regime of the northern Andaman Sea thus exports most sediment offshore despite the large load of the Ayeyawady River.

National Category
Geosciences, Multidisciplinary Geology
Identifiers
urn:nbn:se:uu:diva-358385 (URN)10.5194/esurf-6-451-2018 (DOI)000434957800001 ()
Available from: 2018-08-29 Created: 2018-08-29 Last updated: 2018-08-29Bibliographically approved
Li, G., Madsen, D. B., Jin, M., Stevens, T., Tao, S., She, L., . . . Chen, F. (2018). Orbital scale lake evolution in the Ejina Basin, central Gobi Desert, China revealed by K-feldspar luminescence dating of paleolake shoreline features. Quaternary International, 482, 109-121
Open this publication in new window or tab >>Orbital scale lake evolution in the Ejina Basin, central Gobi Desert, China revealed by K-feldspar luminescence dating of paleolake shoreline features
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2018 (English)In: Quaternary International, ISSN 1040-6182, E-ISSN 1873-4553, Vol. 482, p. 109-121Article in journal (Refereed) Published
Abstract [en]

The Ejina Basin in the central Gobi Desert contains the terminal lakes of the Heihe River. Paleoenvironmental changes in the basin are important since its deposits are a significant source of Northern Hemisphere dust. In this study we employed a K-feldspar pIRIR dating technique to date shoreline features <= 940 m at multiple locations in the Ejina Basin similar to 45-50 m above the modern basin floor. Internal checks of luminescence characteristics were employed to test the reliability of the pIRIR dating. In combination with our previously reported stratigraphy and chronology of shorelines at <= 927 m in the Ejina Basin, these results imply that a paleolake was present in the basin prior to similar to 350 ka. Other high stands in the basin occurred at similar to 320-310 ka, 240-180 ka, 120-80 ka, and similar to 5 ka, corresponding to MIS 9, MIS 7, MIS 5 and the mid Holocene (MIS 1), respectively, indicating a strong link with glacial-interglacial cycles. Extensions of the East Asian Summer Monsoon (EASM) during interglacial periods, possibly interacting with the Westerlies, apparently caused higher precipitation and lake formation. The impact of orbital eccentricity on the EASM/Westerlies appears to be responsible for the formation of major lake/desert cycles on the northeastern margin of the Tibetan Plateau.

Keywords
Gobi Desert, China, Luminescence dating, Orbital scale, Lake evolution, Ejina basin shorelines
National Category
Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:uu:diva-358360 (URN)10.1016/j.quaint.2018.03.040 (DOI)000434685000009 ()
Available from: 2018-08-31 Created: 2018-08-31 Last updated: 2018-08-31Bibliographically approved
Zhiwei, X., Stevens, T., Yi, S., Mason, J. A. & Lu, H. (2018). Seesaw pattern in dust accumulation on the Chinese Loess Plateau forced by late glacial shifts in the East Asian monsoon. Geology, 46(10), 871-874
Open this publication in new window or tab >>Seesaw pattern in dust accumulation on the Chinese Loess Plateau forced by late glacial shifts in the East Asian monsoon
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2018 (English)In: Geology, ISSN 0091-7613, E-ISSN 1943-2682, Vol. 46, no 10, p. 871-874Article in journal (Refereed) Published
Abstract [en]

Recent chronological studies have revealed significant site-specific variations in loess sedimentation, which challenge the use of loess deposits as continuous, easily analyzable paleoclimate and dust records. However, the regional comparability of loess sedimentation at subglacial-interglacial time scales has not yet been systematically tested. This study focused on the spatial and temporal variability of loess sedimentation on the Chinese Loess Plateau (CLP) during the last 20 thousand years and found a clear seesaw pattern across the CLP, indicated by rapid dust accumulation at the desert margin and reduced accumulation/less preservation on the main part of the CLP after ca. 15 ka. This spatial inhomogeneity of loess sedimentation at millennial time scales is controlled by various dust transportation, trapping, and postdepositional processes in different geographic settings, which are ultimately attributed to a combined effect of a weakened winter monsoon and enhanced summer monsoon after the termination of Heinrich event 1.

National Category
Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:uu:diva-360502 (URN)10.1130/G45105.1 (DOI)000445256000010 ()
Available from: 2018-09-13 Created: 2018-09-13 Last updated: 2018-10-18Bibliographically approved
Újvári, G., Stevens, T., Molnár, M., Demény, A., Lambert, F., Varga, G., . . . Kovács, J. (2017). Coupled European and Greenland last glacial dust activity driven by North Atlantic climate. Proceedings of the National Academy of Sciences of the United States of America, 114(50), E10632-E10638
Open this publication in new window or tab >>Coupled European and Greenland last glacial dust activity driven by North Atlantic climate
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2017 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 114, no 50, p. E10632-E10638Article in journal (Refereed) Published
Abstract [en]

Centennial-scale mineral dust peaks in last glacial Greenland ice cores match the timing of lowest Greenland temperatures, yet little is known of equivalent changes in dust-emitting regions, limiting our understanding of dust−climate interaction. Here, we present the most detailed and precise age model for European loess dust deposits to date, based on 125 accelerator mass spectrometry 14C ages from Dunaszekcső, Hungary. The record shows that variations in glacial dust deposition variability on centennial–millennial timescales in east central Europe and Greenland were synchronous within uncertainty. We suggest that precipitation and atmospheric circulation changes were likely the major influences on European glacial dust activity and propose that European dust emissions were modulated by dominant phases of the North Atlantic Oscillation, which had a major influence on vegetation and local climate of European dust source regions.

National Category
Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:uu:diva-337560 (URN)10.1073/pnas.1712651114 (DOI)000417806200007 ()29180406 (PubMedID)
Funder
European Social Fund (ESF), EFOP-3.6.1-16-2016-00004EU, European Research Council
Available from: 2018-01-02 Created: 2018-01-02 Last updated: 2018-02-23Bibliographically approved
Zeng, L., Lu, H., Yi, S., Stevens, T., Xu, Z., Zhuo, H., . . . Zhang, H. (2017). Long-term Pleistocene aridification and possible linkage to high-latitude forcing: New evidence from grain size and magnetic susceptibility from loess-paleosol record in northeastern China. Catena (Cremlingen. Print), 154, 21-32
Open this publication in new window or tab >>Long-term Pleistocene aridification and possible linkage to high-latitude forcing: New evidence from grain size and magnetic susceptibility from loess-paleosol record in northeastern China
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2017 (English)In: Catena (Cremlingen. Print), ISSN 0341-8162, E-ISSN 1872-6887, Vol. 154, p. 21-32Article in journal (Refereed) Published
Abstract [en]

Loess deposits are regarded as good indicators of the inception and development of arid and semi-arid climate in central Asia and northern China during the late Cenozoic. In northeastern China extensive loess deposits are found surrounding the Horqin and Otindag sand fields, and they have great potential for reconstructing the long-term aridification history of the region. However, these loess deposits are currently poorly understood. Here, we present a high-resolution magnetic susceptibility (MS) and grain-size record spanning the last 1.0 Ma from a 36.6-m-thick loess-paleosol sequence at Niuyangzigou site (NYZG) in NE China. The grain-size record reveals a long-term drying trend in NE China since ca. 1.0 Ma, punctuated by two significant abrupt drying events at similar to 0.65 Ma and similar to 0.3 Ma. These results demonstrate a process of stepwise intensification of drying in NE China over the past 1 Ma, and lend support to the hypothesis that global ice volume/temperature changes were the major driver of the long-term aridification of Asian dust source areas. However, unlike the widely studied loess deposits on the central Chinese Loess Plateau (CLP), the MS record in paleosol units Sl, S2 and S4 from the NYZG site do not show evidence of enhanced monsoon precipitation resulting from decreased global ice volume and the prolonged episodes of interglaciation after the Mid-Pleistocene Transition evident in the ice volume record. We hypothesize that this may be due to differences in the climatic sensitivity of the MS of Chinese loess deposits on a regional scale, rather than to in regional differences in monsoon intensity.

Keywords
Loess, Grain size, Magnetic susceptibility, Geochronology, Paleoclimate, Aridification
National Category
Geosciences, Multidisciplinary Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:uu:diva-317021 (URN)10.1016/j.catena.2017.02.020 (DOI)000400040300003 ()
Available from: 2017-03-09 Created: 2017-03-09 Last updated: 2018-01-13Bibliographically approved
Bate, S., Stevens, T., Buylaert, J.-P., Markovic, S., Roos, P. & Tasic, N. (2017). Pottery versus sediment: Optically stimulated luminescence dating of the Neolithic Vinca culture, Serbia. Paper presented at International Conference on Towards the Reconstruction of Paleoenvironment of Vinca- Belo Brdo, Belgrade, SERBIA, JUN, 2013. Quaternary International, 429, 45-53
Open this publication in new window or tab >>Pottery versus sediment: Optically stimulated luminescence dating of the Neolithic Vinca culture, Serbia
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2017 (English)In: Quaternary International, ISSN 1040-6182, E-ISSN 1873-4553, Vol. 429, p. 45-53Article in journal, Meeting abstract (Refereed) Published
Abstract [en]

Optically stimulated luminescence (OSL) dating was applied to the Neolithic Vinca culture's type-site, Vinca Belo-Brdo, to establish best protocols for routine luminescence dating of similar Holocene sites, critical in understanding Neolithic to Chalcolithic cultural development. Equivalent dose (De) values were investigated for sediment samples using 63-90 mm grains on large and small aliquots, and single-grain laser luminescence (SGLL), and for pottery samples using large aliquots of 4-11 mm grains. The effects of changing water content and the different techniques available to establish radionuclide concentration were explored for their impacts on dose rate (Dr) estimates. Ages for two pottery samples of 6.74 +/- 0.37 ka and 7.04 +/- 0.47 ka are in line with the existing AMS radiocarbon chronology for the site and are regarded as the best dates available. Sediment samples at Vinca show poor signal strength, and the uncertainty over past water content, in addition to the possibility of mixing and/or partial bleaching of the quartz, means that we do not recommend the use of sediment-derived ages at complex archaeological sites such as Vinca. OSL dating of fired pottery however, presents a powerful tool for generating independent chronologies at archaeological sites as well as providing additional constraints for Bayesian age models.

Keywords
Vinca, OSL, Pottery, Single grain, Neolithic
National Category
Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-317910 (URN)10.1016/j.quaint.2014.09.042 (DOI)000397931300006 ()
Conference
International Conference on Towards the Reconstruction of Paleoenvironment of Vinca- Belo Brdo, Belgrade, SERBIA, JUN, 2013
Available from: 2017-03-22 Created: 2017-03-22 Last updated: 2017-04-26Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6662-6650

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